Observation of the Earth Liquid Core Resonance by Extensometers

Abstract-We performed Earth tidal measurements by quartz tube extensometers of the same type at several observatories (Bu­dapest, Pécs, Sopronbánfalva in Hungary and Vyhne in Slovakia). ln this paper, the first attempts to reveal the effect of the Free Core Nutation (FCN) from strain measurements are described. The effect of the FCN on the Pl, Kl, '1'1 and clll tidal waves were studied on the basis of tidal results obtained in four observatories. Effective­ness of the correction of tidal data for temperature, barometric pressure and ocean load was also investigated. The obtained Kl/01 ratios are close to the theoretical values with exception of the Pécs station. We found a discrepancy between the observed and theo­retical Pl/01 values for all stations with exception of the Budapest station. It was found that the difference between the measured and theoretical '1'1/01 and clll/01 ratios was very large independently of correction of the strain data. These discrepancies need further investigations. According to our results, fluid core resonance effects can also be detected by our quartz tube extensometers but correction of strain data for local effects is necessary